Circuit breaker



Ap 1, 1952 G. A. MATTHEWS CIRCUIT BREAKER Original Filed April 18, 1942r A. y i.. 2..: n

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Patented Apr. 1, 1952 UNITED STATES PATENT OFFICE:

CIRCUIT BREAKER George Augustus Matthews, Detroit, Miclp, as-

signor to The Detroit Edison Company, Detroit, Mich., a corporation ofNew York 2. Claims- This invention relates to circuit breakers andparticularly to single-pole circuit breakers capable of a quickinterruption of relatively heavy currents.

This application is a division of my copending application Serial No.439,576, filed April 18, 1942, Circuit Breakers, which matured intoPatent No. 2,443,260 on June 29, 1948, which application was a divisionof application Serial No. 333,875, iiled May 7, 1941, Apparatus forProtecting Power Lines, which matured into Patent No. 2,352,556 on June27, 1944, and was re-issued under No. 22,872 on April 29, 1947. Asstated in the earlier patent, serious damage or complete burn-off ofoverhead insulated conductors occurs even in the case of transientfaults when the protective switch gear is of the prior commerciallyavailable types which cannot open the line in less than about V6 second.The present invention contemplates a reclosing circuit breaker having aninitial opening time substantially lower than that attained orcontemplated by the prior workers in this eld.

An object of the invention is to provide a single-pole circuit breakerin which insulating material forms a cylindrical arc-,extinguishinglchamber of restricted annular cross-section in which an arc is drawnupon the separation of the breaker contacts, the movable contact beingcarried by an operating rod which moves axially in they chamber to openand to close the circuit breaker. A further object is to provide acircuit breaker having the characteristics stated, and which includes anarc-spinning coil for establishing a magneticr field within thearc-extinguishing chamber uponk the opening of the breaker contacts,thereby to move the terminals of the arc around on the arcing contacts,thus minimizing the loss of arcing contact metal by not excessivelyheating the arcing contact metal at any one spot.

'Thesev and other objects and advantages of the invention will beapparent from the following specification when taken with theaccompanying drawings inwhich:

Eig. lis a central section through a` single-pole, oil insulated circuitbreaker embodying the invention;

Fig. 2 is a schematic diagram of the same; and

Fig. 3 is an enlarged fragmentary view of the circuit breaker contacts.K

The circuit breakers contemplated by this invention, as employed for theprotection of the conventional three-phase electrical distributionsystems, are light weight, fully automatic, singlepole circuit breakersthat each includes its own mechanical timing equipment and requires noauxiliary circuits, or devices for full automatic operation. As shown inFigs, 1u and 2J the circuit breaker includes., a Control coil and,voperating coil 8| in, series between terminals 82 83, the operating coil8| being normally shunted by the switch 84 that4 is opened by thecontrol coil 80 against a spring 84. This switch and the main breakerswitch are of the reciprocating rod type as described and claimed in myprior Patent No.

2,167,665, granted August 1, 1939, Circuit Breaker, in which an annulararc-extinguishing chamber is formed by horn ber or other organicmaterial,

The core or plunger 85 of coil 8| is secured` to a metal rod B6 whichcarries the movable contact 81 of the circuit breaker and terminatesinarod 88 of' horn ber, or the like. The stationary breaker contactsinclude a main contact 89 that is normally engaged by the rod 86 or itsmovable Contact 87,A and an arcing contact 80 above and spaced from themain contacts. The arcing contact 90 is connectedY to the main contactB9 through a spiral coil 9| coaxial with the rod 86 and the contacts.The function of the coil 9| is to rotatethe arc that is drawn betweenthe moving contact 8l and the arcing contact 90 when the breaker opens,and the coil is wound in the sense opposite that of the operating coil8|. The shunt or control switch 84 is of simpler design as the arc drawnacross its contacts can be extinguished without the aid of` anarc-spinning coil.

Timing mechanism 92 is provided to delay the second and subsequentopenings of the breaker, but the ii-rst openingY takes place with nodelay. The timing mechanism is indicated generally by the block-'diagramoverlying-the. junction of' the operatingv lever* 93 of switch t4 andthe link 94 that connects leverv 93 to the. armature. 95 ofthe trip coil80. Any desired type of mechanism may be employed to delay the openingof the shunt; switch 84 for intervals of 60 cycles or upward when thefault is still on the line at the first or subsequent closures of thebreaker. The detailed construction lis not illustrated since it forms nopartl of the present invention,

The breaker is housed within a chamber comarising a hollow insulator 96and end. closures 91. 98V of metal that'carry the terminals 82,l83respectively. The insulator is provided with metal sleeves 99 towhich thel closures are bolted, and is recessed to receive amountingbracket |00. A plate Ilil extends across the upper end of the insulator96v and constitutes the support for the control. switch. and the breakera,Ss e1fr 1b.1y. and

the control mechanism is located in the domed closure 97 above the plateMDI. The insulator 9S is preferably filled with oil to approximately thelower face of the plate IBI which supports all of the switch and controlmechanism.

The framework of the breaker assembly includes a series of rods IGZ, ametal plate M33 on which the coil El rests, and a plurality of hornfiber plates or disks EM. Insulating rods IE5 are threaded upon rods HB2to secure the plate 63 against spacing sleeves Edt' on rods M92, androds I02 are threaded upon the rods .HB5 to carry the disks IM. Adashpot for arresting the opening movement of the breaker is formed bythe enlarged lower end 85 of the core t5 and a cylinder |05 that ismounted between the plate Iil and the upper disk iEM. The top portion ofthe cylinder flares inwardly above vent openings that permit a freeescape of oil from within the cylinder during the major part of theopening movement of the rod 85.

The two intermediate plates Itl are separated slightly and are recessedto receive small horn fiber disks IEM' that form the outer wall of thearc-suppressing chamber. The small plates may be replaced when thediameter of the chamber has been appreciably increased by the erosion ofthe horn ber. The arc-spinning coil QI is mounted between the two lowerdisks Ica, and connected between arcing contact il@ that is recessedinto the lower face of the upper disk of this pair and a flanged brasstube tilt' that is bolted to the bottom disk I to support the maincontact assembly. The main contact 89 includes a plurality of arcuatesegments secured to the upper ends of the several sections of alongitudinally slotted tube I of resilient metal. The flanged lower endI lll of the tube Idd is electrically connected to a disk HI by a jumperH2, and the disk I I I is pressed against -a boss on the lower closure88 by springs IIS coiled about guide rods that extend through the flangel It.

The breaker opens against a spring iid, and displaces a ratchet bar I I5into engagement with the wheel I I6 of an escapernent mechanism. The

spring I I4 tends to reclose the breaker as soon as the circuit opensbut the downward motion of the switch rod 86 is delayed bythe escapementmechanism. The escapement may be of known types, including means forlocking the breaker in open position after a predetermined number ofreclosures if the fault is still on the line and means for resettingfrom any point in the schedule of reclosures when the breaker closes ona sound line. The time-delay may be of the customary order of from 30 to60 cycles, but the specific design of the escapement mechanism is not anessential feature of this invention.

The method of operation of the circuit breaker will be apparent from theforegoing description. In the case of a single phase line, a circuitbreaker is connected in series with one side of the line at theterminals 32, 33. An ungrounded threephase rcircuit' can be protected bylocating circ-uit breakers in two of the line conductors.

The tripping value of the circuit breaker may be adjusted as desired butwill usually be set up to 200% or more of the rated current capacity ofY the breaker. The tripping current is determined by the design of thecoil 89 and the adjustment of the reclosing spring 84 of the shuntingswitch 84. l The line current does not flow through the operatingwinding under normal operating conditions, and a heavy and suddencurrent surge flows through the operating winding 8i when the sh-untingswitch 84 opens. The operating winding 8I may therefore be designed todevelop a heavy force for displacing the movable Contact fil at highspeed.

The invention is distinguished from prior circuit breakers of the seriesoperating winding type in that the load current is normally by-passedaround the operating winding. The prior circuit breakers have been opento the objections of serious overheating and coil damage due to thecontinuous iiow through the operating winding of load currentsapproximating but somewhat less than the tripping value. Thisoverheating under overloads short of tripping value is eliminated by thepresent invention as te control coil til need develop only a relativelysmall force to open the shunting switch 85. It is therefore possible,and entirely practical, to design the coil SI to develop suicient forcefor an exceedingly high speed opening of the breaker as the winding SIis subjected only to a momentary current surge of high magnitude. Thereciprocating rod and arcextinguishing chamber construction alsocontribute to high speed operations as a l to 2 inch movement of therod, which movement is sufiicient to separate the breaker contacts andsuppress the arc, is obtained in about 2 to 3 cycles with operatingcoils SI of practical design.

The initial opening of the breaker takes place within an interval thatdepends upon the magnitude of the fault current, as shown graphically bycurve B of Fig. 1 of Reissue Patent No. 22,872, but the subsequentopenings are delayed by the timing mechanism 92 to supply current to apersistent fault for periods of about 30 cycles and upward at an inverserate parallel to that for' blowing of fuses, thereby to blowsectionalizing fuses or to burn the conductors down if there are nosectionalizing fuses, in the case of a persistent fault or to lock-outthe breaker in the open position, if the persistent fault cannot beotherwise cleared from the system.

Time values are stated in cycles on a 60 cycles per second basis sinceit is the usual practice in this art to measure the operating times ofprotective switchgear with oscillographs that generate a timing wave ofthe frequency of the electrical distribution system. The novel apparatushas been tested and used on lines supplied with alternating current of afrequency of 60 cycles per second but the protective methods andapparatus may be used on direct current lines or on alternating currentlines energized at 25 cycles per second or at other frequencies.

The quick acting circuit breakers are particularly useful in protectivesystems, as described in the reissue patent, which include line shortingcontactors for a substantially instantaneous suppression of faultcurrents, but may be used to advantage in any protective system wherehigh operating speed is desirable. The high opening speeds of the newcircuit breakers are attained by making the operating coil 8| a serieselement in the line to be protected, whereby a sudden and heavy currentsurge traverses the coil Si upon the opening of the control switch 84which normally by-passes the line current around the operating coil 8 tThe term operating coil is employed in the following claims to identifythe element which functions, upon energization as just stated, tooperate the circuit breaker to open-circuit condition against theclosing force developed by the spring H4. The heavy power surge foreffecting a quick opening of the circuit breaker is developed by anoperating coil in series with the line but there is no overheating ofthe breaker assembly when the line current is maintained for longperiods at approximately the preselected breaker-opening value, sincethe line current is cy-passed around the operating coil 8| until theline current reaches that value at which the control coil Si) opens theby-pass switch 84.

It is to be understood that the invention is not restricted to theparticular embodiment herein illustrated and described, and that variouschanges that may occur to those familiar' with the design andconstruction of circuit breakers fall Within the spirit of my inventionas set forth in the following claims.

I claim:

1. A circuit breaker comprising an axially movable rod carrying acontact, cooperating contact means including a power contact and anarcing Contact, means including an operating coil to move said rod toseparate the Contact thereof from said contact means, insulatingmaterial surrounding said rod and dening a cylindrical chamber in whichsaid rod reciprocates upon the opening and closing of the circuitbreaker, said insulating material comprising a plurality of disks, eachof said disks having a central opening of a diameter just sucientlylarger in diameter than said rod to provide mechanical clearancetherefor, a pair of adjacent disks being spaced from each other and acylindrical extension of insulating material on said rod and movablethereby into said chamber upon an opening movement of the rod, saidinsulating materials having the property of evolving anarc-extinguishing gas when contacted by an arc, said movable rod, saidmovable contact and said cylindrical insulating material having the samecross-sectional area and being in axial alignment with each other.

2. In a circuit breaker, stationary contact means including a maincontact and an arcing contact, movable contact means including anaxially movable metal rod engageable with said stationary contact, meansincluding an operating coil for moving said rod to separate said movablecontacts from said stationary contacts, an arc-spinning coil connectedbetween said main contact and arcing contact, insulating means enclosingsaid contacts, said insulating means comprising a plurality ofinsulating discs, each of said discs having a central opening of adiameter just sufhciently larger in diameter than said rod to providemechanical clearance therefor, means for spacing adjacent discs fromeach other, a rod of insulating material secured to said metal rod andmovable therewith into the bore or said insulating means upon an openingmovement of said rod, said plurality of superposed discs of insulatingmaterial being recessed, and removable discs of insulating materialmounted in the recess of each of said insulating discs to denne anarc-extinguishing chamber, said arcspinning coil being mounted betweentwo of said discs, said movable rod, said movable Contact and said rodinsulating material having the same cross-sectional area and being inaxial alignment with each other.

GEORGE AUGUSTUS MATTHEWS.

REFERENCES CTEB The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,441,193 Wyman Jan. 2, 19231,883,766 Cox et al Oct. 18, 1932 2,112,033 Lingal Mar. 22, 19382,140,378 Biermanns Dec. 13, 1938 2,192,045 Linde Feb. 27, 19402,231,576 Grosse Feb. 11, 1941 2,365,509 Baker Dec. 19, 1944

